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Geography > Hazardous Earth SG3 > Flashcards

Hazardous Earth SG3 Flashcards

1
Q

Define Earthquake

A

Result from the sudden failure of rock within the lithosphere, as a result of a build up of pressure within the rocks

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2
Q

What are the three stages of making an earthquake?

A

1) Gradual build up of tectonic strain which stores elastic energy in crustal rocks
2) When the pressure exceeds the strength of the fault (a threshold event) the rock fractures
3) This produces the sudden release of energy creating seismic waves

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3
Q

What are the 4 locations earthquakes are concentrated in?

A

Mid ocean ridge at Divergent boundaries, Ocean trench and Island arcs at Convergent boundaries, Collisional zones, Conservative plate margins

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4
Q

Define Focus

A

The point of failure of the rocks, where the stress is suddenly released

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5
Q

Define Epicentre

A

Immediately above the point of failure (focus) on the earth’s surface, where most damage is likely to occur

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6
Q

How deep are shallow focus earthquakes?

A

0-70km

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7
Q

What % of earthquakes have shallow focus depths?

A

75%

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8
Q

How deep are intermediate focus earthquakes?

A

70-300km

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9
Q

How deep are deep focus earthquakes?

A

300-700km

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10
Q

What detects and records seismic waves?

A

Seismometer

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11
Q

What are the three types of wave?

A

Primary (P), Secondary (S) and Surface waves (L)

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12
Q

What can primary (P) waves pass through?

A

Solids and liquids

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13
Q

What can secondary (S) waves pass through?

A

Solids only

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14
Q

How much slower is the S wave than the P wave?

A

1/2 the speed of the P wave

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15
Q

Define Magnitude

A

Refers to the level of energy released by the earthquake

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16
Q

What three scales can be used to assess magnitude?

A

Richter Scale, Moment Magnitude Scale, Modified Mercalli Scale

17
Q

How does the Richter Scale assess an earthquake’s energy?

A

Uses the amplitude of seismic waves to determine earthquake magnitude

18
Q

How does the Moment Magnitude Scale assess an earthquake’s energy?

A

Measures magnitude based on physical movement e.g. size of a fault rupture, amount of slip displacement

19
Q

How does the Modified Mercalli Scale assess an earthquake’s energy?

A

Relates ground movement with impacts that can be seen/felt by anyone in the affected location

20
Q

What are five factors influencing intensity?

A

Distance from epicentre, Depth of focus, Magnitude, Geology, Building standards

21
Q

Define Fault Scarp

A

A small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other

22
Q

Define Normal Fault

A

The result of tension, with rocks displaced downwards relative to the other (FUN)

23
Q

Define Reverse Fault

A

The result of compression, rocks are displaced upwards relative to the other (HUR)

24
Q

Define Strike Slip Fault

A

The result of shear stress, rocks are displaced horizontally

25
Q

What boundary are normal faults found at?

A

Divergent

26
Q

What boundary are reverse fault found at?

A

Convergent

27
Q

What boundary are strike slip faults found at?

A

Conservative

28
Q

What is an example of a rift valley?

A

Great African Rift Valley

29
Q

How was the Great African Rift Valley formed?

A

The thinning of the continental crust as a result of extensional forces from plate movement has resulted in faults and sunken valleys known as a graben

30
Q

Define Escarpment

A

A steep slope or long cliff that forms as an effect of faulting or erosion and separates two relatively levelled areas having different elevations

31
Q

What is the primary hazard of an earthquake?

A

Ground shaking - associated with the high amplitude L waves travelling through the surface layers of the earth

32
Q

What are 4 primary hazards associated with an earthquake?

A

Damage to buildings, Liquefaction, Landslide/Avalanche, Tsunami

33
Q

What are 5 factors which can affect people’s perceptions of earthquakes?

A

Religion, Past experiences, Education, Personality, Wealth

34
Q

How many earthquakes does California have each year?

A

Around 10,000

35
Q

How can you mitigate the event of an earthquake?

A

Nothing can be done to prevent an earthquake

36
Q

How can you mitigate the vulnerability of an earthquake?

A

Monitoring, Community preparedness, Evacuation and Warning, Community adaption, Land use mapping of hazards, Aseismic design, Shut down of utilities

37
Q

How can you mitigate the loss of an earthquake?

A

Emergency aid, Search and rescue, Insurance, Resources to help rebuild

Geography (40 decks)

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